Electric remote control system for underwater wells

ABSTRACT

A fail-safe electrical system for controlling, from a remote location, the operation of hydraulic, pneumatic, and/or electric powered mechanisms, and for measuring pressures, temperatures, and any other parameter transduceable to an electric parameter and indicating the values thereof on a display panel at the remote location. As employed with valves and pressures at an underwater oil, gas, or other fluid well, the system comprises a control station at a suitable surface location, an underwater or subsea station adjacent to the well, a single electric cable interconnecting the two stations, and additional single electric cables from the subsea station to each of the valves to be operated and each of the pressure locations to be monitored. Where the valves, chokes, or other elements of the well are hydraulically or pneumatically powered, the system involves solenoid valves preferably positioned in the subsea station to control the hydraulic or pneumatic pressure delivered to the elements, and where the valves are electrically powered they are controlled by suitable relays in their electric circuit. A specific system for controlling the operation of nine valves and for monitoring five pressures at a well&#39;&#39;s Christmas tree is described, as also is a system for carrying out these procedures on a plurality of wells from a single control station.

United States Patent u 1 Begun et al.

In 3,865,M2 [451 Feb. 111, 1975 ELECTRIC REMOTE CONTROL SYSTEM FOR UNDERWATER WELLS [75] Inventors: Robert A. Begun, Los Gatos; Erik Thuse, Santa Clara; Arthur L. McGee, both of San Jose, all of Calif.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Mar. 8, 1973 [21] Appl. No.: 339,236

Related U.S. Application Data [63] Continuation of Ser. No. 38,656, May 19, 1970,

Primary Examiner-Harold W. Weakley Attorney, Agent, 0'- FirmW. W. Ritt, Jr.; C. E. Tripp n5 VAC (60 CY) [57] ABSTRACT A fail-safe electrical system for controlling, from a remote location, the operation of hydraulic, pneumatic. and/or electric powered mechanisms, and for measurf ing pressures, temperatures, and any other parameter transduceable to an electric parameter and indicating the values thereof on a display panel at the remote location. As employed with valves and pressures at an underwater oil, gas, or other fluid well, the system comprises a control station at a suitable surface location, an underwater or subsea station adjacent to the well, a single electric cable interconnecting the two stations, and additional single electric cables from the subsea station to each of the valves to be operated and each of the pressure locations to be monitored. Where the valves, chokes, or other elements of the well are hydraulically or pneumatically powered, the system involves solenoid valves preferably positioned in the subsea station to control the hydraulic or pneumatic pressure delivered to the elements, and where the valves are electrically powered they are controlled by suitable relays in their electric circuit. A specific system for controlling the operation of nine valves and for monitoring five pressures at a wells Christmas tree is described, as also is a system for carrying out these procedures on a plurality of wells from a single control station.

8 Claims, 14 Drawing Figures Pmaman w 1 i915 3.865.142

SHEET D30}: 14

POWER SUPPLY 4 H (225 VDC) ALL- INDICATOR TUBES -ALL POWER BUFFERS ALL BUFFER STORAGES ALL 800/ DECIMAL DECODER/ DRIVERS ALL "0R" CIRCUITS "AND" CIRCUIT H M POWER SUPPLY s I (4 VDC) o 28Gb 52 7 f 280a, U286 54; 280

282.0.) 1% z'zod m 286a m K 52 U 28 TD 3 U 54 28Gb 284 PATENTEUFEB! 1 ms SHEET U3 BF 14 I THOUSANDS. o v M 80D I HUNDREDS H2 500 2.

TENS B00 252.

5G2 256 54 Sea E A POWER SUPPLY l (CONSTANT CURREN f\ /L l POWER SUPPLY 6 (CONSTANT CURRENT) 434 PUSHBUTTON SWITCHES: 434

\ 0) INT. STATION SINGLE STEP-406 J\ b) INT. STATION AUTO snap-408 H T arm-:5 SYSTEM ACTUATE-SGO I m 4 4 Z62 36 H (H 26 (0) POWER SUPPLY 2 H (I5 v 06) 2232- f \J F'I E 5A PATENT ED 3.865.142

SHEET 100! 14 272a SYSTEM l {SYSTEM 2 g -410 2.76- INDICATOR TUBE 4|2 250 278 POWER S'UI PLY 3 (us v DC) POWER SUPPLY 4 H (225 v DC) }ALL INDICATOR TUBES 250 ALL POWER BUFFERS' ALL BUFFER/STORAGES ALL BCD/DECIMAL DECODER/DRIVERS ALL "0R" cmcurrs 250 "AND" CIRCUIT H (H POWER SUPPLY 5 (4V as) 270 26Gb f 52 282a I fi J -f- TD 2860: 5 A V w I R 282.

5& F'I I3 513 1. ELECTRIC REMOTE CONTROL SYSTEM FOR UNDERWATER WELLS This is a continuation of application Ser. No. 38,656, filed May 19, 1970 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to electric remote control systems, and more particularly to such systems for controlling from a remote location the operation of valves, chokes, blow-out preventers, connectors, and other various funtional elements associated with an oil or gas well, and for reading at the remote location the fluid pressures and temperatures, or any other parameter transduceable to an electric parameter, present at the well. One specific embodiment of the invention is with underwater well Christmas trees and surface-located control stations.

The ever-increasing demand for greater supplies of petroleum and natural gas have caused the worldwide search for these resources to be directed more and more to the continental shelves and other off-shore underwater areas in many locations throughout the world. For some time it has been common practice to drill offshore wells from surface platforms either floating or supported on pilings, etc., and to complete the wells with Christmas trees on these platforms. Such surface completions are undesirable from several standpoints, prominent among which are their hazard to navigation, their vulnerability to damage by storms or other adverse surface climatic conditions, and their negative esthetic appear to certain sectors of the community.

To overcome these problems, equipment and techniques have been developed for completing off-shore wells on the bottom or floor of the water body, but as the water depth increases the problems of controlling the valves and other components at the on-bottom site. and of monitoring the pressures, temperatures, etc. at that site become much greater. Divers and submersible vessels can be used for some of this work, but both are expensive and not infrequently prevented from performing their tasks because of intolerable surface conditions. Divers also are very limited as to the depth to which they can descend and carry out their tasks efficiently, and some of the off-shore wells currently being drilled, as well as some of those under consideration, are in water depths far too great for diver operations.

Controlling the valves of the on-bottom completed well by remote means has been done prior to this invention, but because of the complex equipment employed, the problems of malfunction and even greater problems of correcting the malfunction, and the magnitude of expense, these remote systems have not come into significant use. Remote control systems for surfacecompleted wells, such as on off-shore platforms or on land, also are plagued with the same problems of complexity, malfunction, expense, etc. that prevail beneath the water. Thus there is a genuine need for a remotely controllable, relative uncomplex, and highly reliable system for these purposes, and it is to this end that the present invention is directed.

Accordingly, one of the objects of this invention is to provide a system for remotely controlling the operation of valves, chokes, blow-out preventers, and other functional elements of an oil, gas, or other fluid well.

Another object of the present invention is to provide a system for monitoring at a remote location, thefluid pressures and temperatures, or any other parameter transduceable to an electric parameter, in the annulus, tubing, the bores of the Christmas tree, flow lines, and any other passages of an oil, gas, or other fluid well.

Another object of the invention is to provide a failsafe electric system for controlling, from a remote location, the hydraulic, pneumatic or electric power utilized to open and close the valves, chokes, blow-out preventers, and all other similarly functioning elements of an underwater or surface located oil, gas, or other fluid well.

Still another object of the present invention is to provide a remotely operated, fail-safe control system for manipulating the valves, chokes, blow-out preventers, and other equipment at a plurality of underwater or surface located wells, and for monitoring fluid pressures and other parameters of the wells transduceable to an electric parameter.

A still further object of the present invention is to provide a remotely operated, electric control and monitoring system with dual operating modes, the modes interconnected such that the system can be switched immediately from one to the other in the event either mode malfunctions.

SUMMARY OF THE INVENTION Broadly considered, the present invention comprises an electrical system for remotely controlling the operation of hydraulic, pneumatic, and/or electric powered mechanisms, and for measuring pressures, temperatures, and any other parameter transduceable to an electric parameter, at one location and reading out these measurements at a remote location. In a more specific sense, the invention comprises an electric system for controlling from a surface or otherwise remotely located station the operation of valves, chokes, blow-out preventers, and other manipulatable elements in or at an oil, gas or other fluid well, and for monitoring at the station the position of the valves and the fluid pressures, temperatures, etc. present in or at the well. The system controls the operation of the hydraulic and pneumatic powered valves, chokes, etc. through sole-.

noid valves in the hydraulic or pneumatic lines, and controls electric powered valves, chokes,'etc. through suitable relays or switches in their electrical power lines. In the described embodiments of the invention, the pressures, temperatures, etc. are transduced as resistances and these resistances read out as visually displayed numerical values. The invention includes a system for controlling and monitoring a single well, comprising a control station with a display panel for reading out the various conditions being monitored at the well, and a subsea station, adjacent the well, for housing the systems well-site components. The invention also includes a similar system for carrying out these same operations on a plurality of wells, in which case a separate subsea station is provided for each well and a single intermediate switching station is incorporated between these subsea stations and the surface station.

The stations are connected by a cable containing electrical conducting lines, the cable from the surface station to the intermediate station containing six conductors, and from the surface station or the intermediate station to the subsea station containing four conductors. Each of the valves of the tree, or of the several trees when more than one is involved, can be opened or closed and its position determined separately from the others, and each of the fluid pressure, temperature or other transducer measurable parameters of the tree or trees can be read separately at the surface. The electrical system is connected to the valves, etc. such that it provides fail-safe operation thereof; thus if the system should malfuntion, all of the valves, etc. will automatically move into their fail-safe position. Both the single tree and the multiple tree sytems of the invention include a redundant or backup mode to which the system can be immediately switched in the event the primary mode malfunctions. No separate subsea power supply is required for the operation of the systems of this invention, for all operating power requirements are met by a surface source of electric power, such as l 15 volts AC.

- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic illustration, partly in perspective and in section, of a system for controlling nine valves and reading five pressures at a single underwater oil or gas well Christmas tree according to this invention, including a representation of one form of display and control panel that could be used at the surface station.

' FIGS. 2A through 2E, when properly positioned together, constitute a partial block, partial schematic representation of the electrical circuitry of the surface station in the system of FIG. 1.

FIG. 3 is a partial block, partial schematic representation of the electrical circuitry of a subsea station according to this invention.

FIG. 4 is a diagrammatic illustration, partly in perspective and in section, of a modified form of the system of FIGS. l3 for use in controlling the valves and reading the pressures at five Christmas trees from a single surface station.

FIGS. 5A through 5E, when properly positioned together, constitute a partial block, partial schematic representation ofa portion of the electrical circuitry of the surface station in the system of FIG. 4.

FIG. 6 is a partial block, partial schematic representation of the electrical circuitry of the intermediate station of the system of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS SINGLE WELL SYSTEM FIGS. 1, 2A through 2E, and 3 illustrate a system 10 within the scope of this invention for controlling the operation of nine valves of, and monitoring pressures at five locations at, a single underwater oil, gas, or other fluid well. As FIG. 1 diagrammatically illustrates, this system 10 includes a control station 12 positioned at a suitable location, such as a land based facility, offshore floating platform, or other surface location, a subsea station 14 positioned adjacent the wellhead 16, a four-conductor electrical cable 18 connecting the control station 12 with the subsea station 14, a threeconductor electrical cable 20 connecting the subsea station with each of nine valves V1-V9 on the wells Christmas tree 24, and a two-conductor electrical cable 26 interconnecting the subsea station 14 with each of five transducers Pl-PS for measuring the pressure at the chosen location on the Christmas tree 24.

The system illustrated in FIG. I is designed to control two master valves V1 and V2 in the annulus bore of the tree, two master valves V3 and V4 in the first tubing bore, a wing valve V5 for this bore, two master valves V6 and V7 and a wing valve V8 in the other tubing bore, and a crossover valve V9. Pressure transducer PI is positioned to respond to the pressure in the annulus bore between master valves VI and V2. Pressure transducer P2 is positioned intermediate the master valves V3 and V4, and pressure transducer P3 is positioned intermediate the master valve V4 and the wing valve V5, to register the pressure at those intermediate points in the first tubing passage. Likewise, pressure transducer P4 is intermediate the master valves V6 and V7, and transducer P5 is intermediate the valves V7 and V8, to monitor the pressures in the second tubing passage. These relative positions of the valves VI through V9, and the pressure transducers Pl through P5, are pictorially illustrated in the display panel 42 of the control station 12 in FIG. 1, wherein the annulus bore is shown at 30, the first tubing bore is shown at 32 and its flow line connection at 34, and the second tubing bore and its flow line connection are illustrated at 36, 38, respectively. The line 40, in which the crossover valve V9 is mounted, serves as a crossover passage between the lines 34, 38, and, of course, also between the flow lines 34a, 38a connected to these lines 34, 38.

The control stations display panel 42 includes the several components for visually indicating the condition of each of the valves V1 through V9, and the pressures at each of the pressure transducers Pl through P5, to faciliate proper control of the various tree functions by the operator. This display panel includes a valve identification light 44 for each of the valves V1 through V9 and associated therewith a valve indicator tube 46, such as a gas filled cold cathode indicator tube known in the art as a Nixle tube, which indicates the present position of the valve with which it is associated. In like manner, the display panel 42 includes a pressure identification light 48 and a pressure indicator tube 50, of the same type as tubes 46, for each of the pressure transducers Pl through P5 on the tree 24. As will be more fully described, this control system is designed to facilitate the updating of the information shown in the valve and pressure indicator tubes by a manual or automatic scanning operation, so that at any time the operator can observe the present condition of these elements and pressures by reading the display panel. The valve and pressure indicator lights are also designed to indicate the present position of the scan, thereby providing the operator with information as to what next must be done.

The display panel 42 also includes a single-step pushbutton switch 52 for manually controlling the scan of the valves and the pressure transducers, and an autostep push-button switch 54 that, when depressed, causes the scan to be carried out automatically in a cyclic fashion through all of the valves and pressure transducers. The display panel 42 further includes a valve actuate push-button switch 56 for actuating the system to open or close a particular valve, a valve actuate indicator tube 66 to indicate what can be done to the valve at that time by pressing the switch 56, and a system change push-button switch 58 with mode identifying S1 and S2 indicator lights 60, 62, respectively, for changing the polarity of the system and indicating which of the two polar states or modes the system is on, i.e., the main system mode S1 or the redundant or backup system mode S2.

, The system also includes a key locking switch 64 for preventing or permitting a valve operation to be executed when the valve actuate switch 56 is depressed. A power switch 68 in the external 115 volt AC power line 70 is also included in the display panel 42, together with a light 72 for indicating whether the power is on or off, the switch facilitating turning the power on or shutting it off as desired. Thus it is apparent that the display panel 42 and the surface station 12 simulates the subsea Christmas tree 24 with respect to the present condition of the several valves and the pressure transducers to which the system is connected, and affords the operator a means for quickly and accurately determining the conditions at the Christmas tree and opening or closing the connected valves as he desires.

Operation and control of the valves at the tree 24, and monitoring the pressures of the pressure transducers P1 through P5 at the tree, are achieved through a unique and highly simplified electrical system that is schematically illustrated in FIGS. 2A through 2E, and 3. That part of the system existent at the surface control station 12, including the circuits, lights, indicator tubes, etc., of the display panel 42, is shown in FIGS. 2A through 2E, so that when these Figures are properly placed together they represent the total circuitry of the control station 12. The components and circuits of the subsea station 14, and of the valves V1 through V9 and the pressure transducers P1 through P5, are shown in FIG. 3. Thus, when FIGS. 2A through 215 and 3 are placed together they form the complete circuit diagram of the system for a single well according to this inventron.

Referring first to FIG. 2A, external 115 volt AC cycle power is brought into the surface station 12 by a line and connected to a digital volt meter (DVM) that supplies a direct current output in the form of tens, hundreds and thousands binary coded decimal (BCD). A four-conductor line 82 connects the thousands BCD output of the DVM 80 to a BCD-to-decimal decoder driver 84 (FIG. 2C), such as a CIA-L 9960 (available from Fairchild Semiconductor Division of Fairchild Camera and Instrument Corporation) that accepts 1-24-8 binary coded decimal inputs at integrated circuit signal levels and produces ten mutually exclusive outputs that can directly control the ionizing potentials of many gas filled cold cathode indicator tubes. Lines 86, 88, 90, 92 and 94 separately connect five outputs of decoder driver 84 to the identification lights 48 of pressure transducers Pl through P5, respectively, and lines 96, 98, 100, 102 and 104 connect these same five outputs to the valve actuate indicator tube 66 to indicate when a pressure is being monitored. The nine identification lights for valves V1 through V9 (FIG. 2C) are likewise connected by lines 106, 108, 110, 112, I14, 116, I18, and 122 to nine separate outputs of a second BCD-to-decimal decoder driver 124. Lines 126, 128, and 132 separately connect four OR circuits 134, 136, 138 and 140 to the four inputs of decoder driver 124, and each of these OR circuits is connected by a line 142 to a single AND circuit 144 that is connected to two additional outputs of the decoder driver 84 by lines 146, 148. These two additional outputs are also connected to the valve actuate indicator tube 66 by lines 150, 152.

Since the pressures at the Christmas tree normally are read out as thousands and hundreds of pounds per square inch (psi), the hundreds BCD output of the DVM 80 is connected by a four conductor line 154 through a power buffer 156 (FIG. 2D) to sub-circuits 158, 160, 162, 164 and 166 for each ofthe pressure indicator tubes for transducers P1 through P5, respectively. Each of the circuits 160, 162, I64 and 166 is identical with circuit 158 which includes, in series with line 154, a buffer storage 168 such as a CpLL 9959 Buffer Storage Element (available from Fairchild Semiconductor Division of Fairchild Camera and Instrument Corporation) that consists of four gated-latch circuits and a common gate driver, a BCD-to-decimal decoder driver 170, and a pressure indicator tube for the pressure being monitored, in this case tube 50 for pressure at transducer P1. In like manner, the pressure in hundreds is indicated in the pressure indicator tubes by signals from the tens BCD output of the DVM 80, which signals are conveyed by a four conductor line 172 through a power buffer 174 to each of the circuits 176, 178, 180, 182 and 184. The circuit 176, with which each of circuits 178, 180, 182 and 184 are iden-' tical, includes in series a buffer storage 186, a BCD-todecimal decoder driver 188, and the pressure indicator tube 50. Each of these pressure indicator tubes is connected to its corresponding identification light 48 by lines 190, 192, 194, 196 and 198, respectively. These lines 190, 192, 194, 196 and 198 connect the corresponding decoder driver 84 output terminals for the pressure transducer Pl-PS identification lights to the corresponding buffer storages 168 in the circuits 158, I60, I62, I64 and 166, and also to the buffer storages 186 of the circuits 176, 178, 180, 182 and 184.

Thus the line 190 functions tell the buffer storages 168 and 186 to store the last received data until they are in position to receive new data regarding the pressure at pressure transducer P1, and the lines 192, 194, 196 and 198 perform identical functions with their corresponding buffer storages. Accordingly, when a signal is directed to the identification light 48 for transducer P1, this signal also is sent to buffer storages I68 and 186, with the result that this identification light illuminates and the pressure indicator tubes 50 for P1 update the data displayed to indicate the present pressure at P1. When a signal is directed to any of the other identification lights of P2-P5, or for that matter of valves Vl-V9, the identification light of P1 does not illuminate and the line 190 tells buffer storages 186 and 168 not to change output regardless of any change of input.

The OR circuits 134, 136, 138 and 140 are connected in parallel by a line 200 to the power buffer 156 which, of course, serves to increase the current supplied to the OR circuits, and also to the circuits 158, I60, 162, I64 and 166, from that supplied to it by the hundreds BCD output of the DVM 80.

Each of the valve indicator tubes 46 is connected through its individual circuit to the line 172 from the tens BCD output of the DVM 80. As illustrated in FIG. 2E, the valve indicator tube 46 for valve V1 is designed to indicate an 0 when the valve: is open, a C when the valve is closed, and an M" when the valve is moving between opened and closed positions, these indicia appearing on the tube in response to a current received in the tube from line 172 through serially connected buffer storage 204, BCD-to-decimal decoder driver 206, and discreet resistors R1 through R9. These resistors are grouped together in threes, with resistors R1, R2 and R3 connected in parallel to the decoder driver 206 and the contact of the indicator tube 46 for the indicia 0. Likewise the resistors R4, R5 and R6 are connected in parallel between the decoder driver 206 and the C" input contact of the indicator tube 46, and resistors R7, R8 and R9 are connected in parallel between the decoder driver 206 and the M contact of the tube 46.

Similar to the interrelation between the pressure identification lights 48 and the pressure indicator tubes 50, each of the nine outputs of the BCD-to-decimal decoder driver 124 (FIG. 2C) going to the nine valve identification lights 44 is also connected to the buffer storage for the corresponding valve indicator tube, for example, line 106 from the BCD-to-decimal decoder driver 124 to the valve V1 identification light is connected by a line 208 to the buffer storage 204. In like manner, lines 210, 212, 214, 216, 218, 220, 222 and 224 interconnect lines 108, 110, 112, 114, 116 118, l20 and 122, respectively, with the buffer storages of the valve indicator tubes for valves V2 through V9, respectively. These lines 208-224 perform the same function for these valve identification lights and indicator tubes as do the lines 190-198 for their pressure identification lights and tubes. Accordingly, when the valve V1 identification light is illuminated the indicator tube for valve V1 is receiving new'data, the valve identification lights for valves V2-V9 are off, and the indicator tubes for valves V2-V9 show the last received data from their respective valves. it is to be understood that the components of the subcircuit 202 are duplicated for each of the valve indicator tubes of the remaining eight valves V2 through V9, i.e., subcircuits 226, 228, 230, 232, 234, 236, 238 and 240.

Connected to the 115 volt AC power line 70 is a bus line 250 for providing power to the various components shown in FIGS. 2A and 28 on the control portion of the control station 12. These components include a power supply No. l for providing a constant current to the subsea sation 14, a power supply No.2 for providing l volt direct current to the subsea station 14, a power supply No. 3 for providing 1 volts direct current to the subsea station 14, a power supply No. 4 for providing 225 volts direct current to each of the valve and pressure indicator tubes, and a power supply No. 5 for providing four volts direct current to each of the power buffers, the buffer storages, the BCD-to-decimal decoder drivers, the OR circuits, and to the AND circuit 144. Two lines 252, 254 in the four conductor electrical cable 18 are connected to the DVM 80, the line 254 running through the normally closed contact 56a of the valve actuate switch 56, and also including a variable resistor 256. Variable resistor 256 allows adjustment of the total resistance seen by the constant current power supply to account for different lengths of cable between the surface station and the subsea station. The positive side ofthe power supply No. l is connected by line 258 to the conductor 252, and the negative side of the power supply No. l is connected by line 260 to the conductor 254. A line 262 connects the common terminal of the power supply No. 2 to the conductor 254, and a line 264 connects parallel leads 266, 268 from the negative and positive contacts of the power supply No. 2 to the conductor 252. The lead 268 includes the normally open contact 56b of the valve actuate switch 56, and lines 266 and 268 go through a single poledouble throw contact of a double pole-double throw relay 270.

In order to provide a back-up for the system in the event of malfunction of any of the components at the subsea station or the Christmas tree, this invention includes the facility for reversing the polarity of the 1 15 volts direct current conducted through conductors 272, 274 in the cable 18 to the subsea station. This polarity reversal is achieved by operation of the system change switch 58 that. as seen in FIG. 2A. is positioned between the output leads 276, 278 of the power supply No. 3 and the conductors 272, 274. Accordingly, as is shown in FIG. 2A, when the switch 58 is positioned so that the control system is functioning in the system one (S1) mode the positive lead 276 is connected to conductor 274, and negative lead 278 is connected to the conductor 272, with the S1 identification light 60 illuminated. When the switch 58 is switched to the S2 position, the positive lead 276 then is connected to the conductor 272, the negative lead 278 is connected to the conductor 274, and the S2 identification light 62 is illuminated.

The single-step switch 52 is a momentary contact push-button which will advance the switching module (described later) of system 1 or system 2 one stop. As shown in FIG. 2B, time delay relays 280, 282 and 286 delay upon energizing of their coils, whereas time delay relay 284 delays upon deenergizing of its coil.

When the single step switch is actuated time delay relays 284 and 286 are actuated. Normally open time delay relay contact 284a is immediately closed which locks up the output of DVM so that the changes in input to this DVM during the switching period will not cause false information to be sent to the valve and pressure indicator tubes.

After lock up is in progress, time delay relay 286' times out and closes its normally open contacts 286a and 286b. Thus 286b energizes relay 270 which closes contacts 270a and transmits a negative 15 volt signal down wire 252 through contact 326-2 to one side of the relay 312. The common voltage of power'supply 2 feeds through wire-254 through diode 320 and zener diode 324 to the other side of the coil of relay 312. This 15 volts applied to the relay 312 actuates the relay which closes contact 312-1, energizing stepper coil 3020 and cocks the stepping switch. When time delay relay 286 timed out, it also closed its contact 286a which actuated time delay relay 280. Time delay relay.

282 is not actuated as contact 270a of relay 270 was opened when relay 270 was actuated by relay contact 286b of relay 286. Time delay relay 280 now times out opening contact 280a which deactuates time delay relay 286. This deactuates relay 270 removing the negative 15 volts from relay 312 in FIG. 3, thus deactuating the coil 302a of the stepper switch and the stepping switch steps to its next position. The opening of contact 286a also deactuates time delay relay 280. Next, time delay relay 284, which has the longest time delay of all, times out, opening contact 284a which allows DVM 80 to process information from the new position of the stepping switch. Relays 270, 280, 282, 284 and 286 are all deactuated and the single step switch can be pressed to repeat the stepping process if desired. Time delay relay 282 did not perform any function in the single step switching process.

When the auto step switch S4, which is a maintained contact switch, is actuated time delay relays 284, 280 and 286 are actuated. Time delay relay 284 again locks up the DVM 80 as in the single step switching. After time delay relay 286 times out, relay 270 is actuated which cocks the stepping switch as in the single step switching. Time delay relay 280 is also actuated when time delay relay 286 times out. After time delay relay 280 times out, time delay relay 286 is deactuated which deactuates relay 270 and the stepping switch steps to its next position as in the single step operation. When time delay relay 280 timed out it deenergized time delay relay 284. As relay 284 has a time delay after deenergizing this starts its timing cycle. When relay 270 deactuated, its normally closed contact 270 allowed time delay relay 272 to be actuated through the main tained contact of auto step switch 54. Time delay relay 284 now times out, unlocking DVM 80 so that it can process the information from the new stepping switch position. After time delay relay 282 times out, its normally closed contact 282a deactuates time delay relay 280. This closes contacts 280b and 280a which actuates time delay relay 284 and 286 and the sequence starts again. It will repeat until auto step switch 54 is released at which time it will complete the cycle it is on and stop.

One of the key features ofthe present invention is the provision of a switching module at the subsea station 14 to sequentially connect the surface station to each of the valves or other wellhead elements to which the system is connected, and then to the analog functions, i.e., the pressure transducers, employed for measuring the pressures, temperatures, or any other parameter which can be transduced to a resistance. As illustrated in FIG. 3, the switching module 300 comprises a pair of twodeck stepping switches 302, 304 having stepping coils 3020, 3040, respectively, and these switches 302, 304 are connected to the conductors 252, 272 in the cable 18. Stepping switch 302 is functional when the system l-system 2 switch 58 is in the system 1 position, as illustrated in FIG. 2A, and stepping switch 304 functionally replaces stepping switch 302 when switch 58 is placed in the system 2 position, thereby reversing the polarity of the 115 volt direct current (DC) in lines 272 and 274 but maintaining the same polarity in lines 272b and 27% below contacts 326-5 through 326-8. Thus the stepping switches 302, 304, in conjunction with the system l-system 2 switch 58, provide a back-up facility should either of systems 1 or 2 malfunction.

Decks 302a and 304a of the stepping switches 302, 304 each contain 18 contacts or switch positions, two positions for each of the valves V1-V9, with one of each pair of positions functioning to conduct current for opening the valve and the other position of the pair for closing the valve. The positions are arranged in alternate order sequentially on the decks 302a, 304a, so that when the switch is in the odd positions 1, 3, 5, etc., the valve to which the particular position is connected is conditioned for opening, and when the switch is in any of the even number positions 2, 4, 6, etc., the valve is conditioned for closing. The decks 302b, 304b of the stepping switches contain 23 contact positions, the first 1 l8 affording sequential connection with the resistances connected to the valve limit switches to indicate valve position, and the last five affording sequential connection with the five pressure transducers P1-P5, respectively. Thus, when the switch is on position 19 a circuit is completed with pressure transducer P1, etc., with the last position 23 affording a circuit through pressure transducer P5.

The stepping switches 302, 304 are ope rated through step-actuate decoder modules 306, 308. The decoder module 306 includes a relay coil 310 for the relay contacts 310-1 of deck 302a, a relay coil 312 for the relay contacts 312-1 of the deck 302a, diodes 314, 316 and zener diode 318 associated with the relay coil 310, diodes 320, 322 and zener diode 324 associated with the relay coil 312, and two contacts 326-1, 326-2 of a four pole, double throw relay 326. Similarly, decoder module 308 includes coil 328 of a single pole, single throw relay with contacts 328-1, a coil330 of a single pole, single throw relay with contacts 330-1, diodes 332 and 334, and zener diode 336 associated with the coil 328, diodes 338, 340 and zener diode 342 associated with the coil 330, and contacts 326-3 and 326-4 of the relay 326.

These step-actuate decoder modules 306, 308 accept a plus or minus fifteen volt DC signal from the conductors 252, 254 of the cable 18, and function to advance the switching module or open and close the valves.

When the polarity on line 252 is a positive 15 volts relay 310 is actuated, contact 310-1 is closed and 1 15 volts DC is applied through stepping switch deck 302a to open or close a valve. When the polarity on line 252 is a negative 15 volts relay 312 is actuated, contact 312-1 is closed and volts DC is applied to stepper switch coil 302C to cock the stepping switch. When the negative 15 volts is removed from line 252 the stepping switch coil 302 is deenergized and the stepping switch advances to the next position.

Relay 326, which is operated by a positive 115 volt DC signal on the conductor 272 of the cable 18 coming from the surface station system l -system 2 switch 58, governs which decoder module 306, 308 is functionally included within the over-all control system at a given time, and hence which stepping switch 302, 304 will be employed to operate the valves V1-V9 and monitor the pressure transducers Pl-PS.

Using the conditions of FIG. 3 to illustrate, when a l5 volt signal is introduced into the conduit 252 by pressing the surface station actuate switch 56, this signal is received by decoder module 306 and energizes either the relay 310 which allows 115 volts to open or close the valve, or the relay 312 which advances the stepping switch one step.

In this embodiment of the invention, the valves V1-V9 are shown as hydraulically powered, and the control of their operation is facilitated by the functioning of a solenoid valve 350-1, etc., in their hydraulic lines. It should be understood that pneumatic or electric powered valves also can be controlled with the system of this invention, the pneumatic in the same manner as the hydraulic, and the electric by means of a suitable relay or the like in the circuit to its motor.

The control of these solenoid valves, and also the manner by which the position of the valves Vl-V9 can be determined, is illustrated in FIG. 3 which depicts the circuitry to valves Vl-V9. Referring to the illustrated circuit for valve V1, the solenoid valve 350-1 positioned in the hydraulic line 352-11 is connected to the system l-system 2 115 volt direct current circuit by lines 354-1, 356-1 that connect with relay contacts 326-5, 326-6, 326-7, and 326-8, which in turn are connected to conductors 272, 274. A double pole, single throw relay 358-1, with one set of contacts 358-1a in the line 356-1 and the other set of contacts 358-1b in a line 360-1 that interconnects the lines 356-1 and 354-1 and includes the relay 358-1, is operatively connected to the first and second positions of the stepping switch decks 302a, 304a by lines 362-1, 364-1, respectively. This valve operating subcircuit also includes a 

1. In a fluid well flow control apparatus having a system for remotely controlling the operation of electrically energized mechanisms wherein said mechanisms have a plurality of operational states, and for measuring and reading out the operational state of each of said mechanisms, said system including a control station connectable to a source of electrical power, electrical circuit means at said control station with display means having indicators for individually selectively indicating the operational state of said mechanisms, a switching station in the vicinity of the fluid well, first means including electric conductors for electrically interconnecting the control station and the switching station, and second means including electric conductors for individually electrically interconnecting the switching station with each of said electrically energized mechanisms, the improvement comprising: a. said selective indication means having a corresponding selective response to each one of a plurality of differing predetermined voltages present in one of said electric conductors, b. a plurality of resistors interconnected with said mechanisms for providing said differing predetermined voltages, c. means for selectively interconnecting said resistors in response to control of said mechanisms to produce said predetermined voltages on said conductor, and wherein, d. said plurality of resistors include first, second and third resistors, wherein said first and third resistors are selectively connected in parallel by said selective interconnecting means to provide a predetermined voltage indicating a first limit of operation of said mechanism, said second and third resistors are selectively connected in parallel by said selective interconnecting means to provide a differing predetermined voltage indicating a second limit of operation, and said third resistor alone provides a further differing predetermined voltage indicating a third state of operation when said first and second resistors are disconnected therefrom, thereby to effect display at said control station of the particular operational state of the well control mechanisms with a minimum of conductors interconnecting said mechanisms and said control station.
 2. A system according to claim 1 wherein each indicator includes indicia for indicating three operational positions of the mechanism to which it is related, including the opposite limits of operation and a state of operation in between said limits.
 3. The improved system of claim 1 wherein said controlled mechanisms include valves, and wherein said states of operation thereof comprise respectively: valve open, valve closed, and valve intermediate position.
 4. The improved system of claim 3 wherein said states of operation of said well control apparatus further include temperature and pressure parameters.
 5. A system according to claim 1 wherein said mechanism includes first and second limit switches, and wherein said first resistor is in series with said first limit switch, said second resistor is in series with said second limit switch, and said third resistor is connected across the series combination of said first and second limit switches, and their respective resistors, whereby when the mechanism is somewhere in between its limits of operation neither limit switch is closed and said third resistor only can then be measured externally.
 6. A system according to claim 1, including a further plurality of resistors and at least one transducer means for measuring temperature or pressure at said well flow control apparatus, such that said display means indicates the measured temperature or pressure in response to specific voltages conducted from said measuring means to said display means.
 7. A system according to claim 1 wherein said electrically energized mechanisms are valves, and wherein said well flow control apparatus is an underwater Christmas tree, including the further improvement wherein said first interconnecting means comprises a four-conductor electrical cable between the control station and the switching station, wherein said second interconnecting means comprises a three-conductor electrical cable between the switching station and each valve, and wherein said switching station includes means to switch from one valve to another upon command from the control station.
 8. A system according to claim 1, including a plurality of separate fluid well flow control apparatuses each having its own switching station, and an intermediate station between the control station and said switching stations, the further improvement wherein the first interconnecting means comprises a six-conductor cable between the control and intermediate stations, and a four-conductor cable between the intermediate station and the switching stations, and wherein the second interconnecting means comprises a three-conductor cable between the switching stations and their related well flow control apparatuses. 